In the field of liquid crystal display (LCD) panel, a light emitting diode (LED) used as a light source of a backlight has advantages of energy saving and environment protection in comparison with a cold cathode fluorescent lamp (CCFL), so that the trend of development of the backlight is using the LED to replace the CCFL. However, the important factor influencing the development of LED is a problem of heat-dissipation. Specially, the side light type LED backlight module is violently influenced by the temperature. For optical effect, the side light type LED backlight module must keep a stable gap of light coupling between the light source and the light guide plate, but when the LED is lighted on, the air in the backlight module is heated by a heat generation of the LED, and the temperature of a light guide plate in the backlight module is quickly ascended by the heat conduction of the air.
For descending the inner temperature in the backlight module, a heat sink is generally used for dissipating the heat of the light source, but it is still unable to solve the temperature problem of the internal air in the backlight module. Besides, the developing trend of the backlight module includes design directions of ultra-thinning and narrow frame edge, and the design which only dissipates heat by the heat sink is difficult to effectively descend the inner temperature of the backlight module. Hence, the thermal expansion of the light guide plate in the backlight module is increased, so it causes an optical problem, such as a non-uniformity of backlight of display due to a surface unevenness of the light guide plate.